Glycerol was converted with (MeO)(2)CH(2) to a mixt. of 3-hydroxydioxane (94%) and 2-hydroxymethyldioxolane at 100-110 degrees C and overpressure 0.5 MPa for 1.5 h in presence of p-MeC(6)H(4)SO(3)H, MeSO(3)H and a macroporous ion-exchange resin catalysts. The product was sepd. by distn., the unconverted raw materials were recycled. The best results were achieved when the ion exchange resin was used as catalyst (product one-step yield about 56%, purity 99.92%).